Solar receiver

ABSTRACT

A solar receiver includes a manifold, a sealed enclosure around the manifold and a plurality of tubes connected to the manifold and extending through the sealed enclosure.

BACKGROUND

This disclosure relates to improvements in solar receivers.

A concentrated solar power tower system collects solar radiation for the purpose of heating a working fluid to generate electrical power. The system typically includes solar receivers that are mounted on a tower. Heliostats direct concentrated solar radiation toward the solar receivers. The solar radiation heats working fluid that circulates through tubes of the solar receivers.

SUMMARY

A solar receiver according to an exemplary aspect of the present disclosure includes a manifold, a sealed enclosure around the manifold, and a plurality of tubes connected to the manifold and extending through the sealed enclosure.

In a further non-limiting embodiment, the sealed enclosure defines a volume between the sealed enclosure and the manifold, the sealed enclosure substantially sealing the volume from convective air flow between the volume and an exterior of the sealed enclosure.

In a further non-limiting embodiment of any of the foregoing examples, the volume is at a lower pressure than the exterior.

In a further non-limiting embodiment of any of the foregoing examples, the volume includes an insulating gas different than air.

In a further non-limiting embodiment of any of the foregoing examples, the insulating gas is selected from the group consisting of nitrogen-based gas, helium-based gas, carbon dioxide-based gas and combinations thereof.

In a further non-limiting embodiment of any of the foregoing examples, the sealed enclosure includes at least one seal element.

In a further non-limiting embodiment of any of the foregoing examples, the sealed enclosure includes at least one seal element between a panel of the sealed enclosure and the plurality of tubes.

In a further non-limiting embodiment of any of the foregoing examples, the sealed enclosure includes a top wall above the manifold, a bottom wall below the manifold, a forward wall in front of the manifold, a back wall behind the manifold, and side walls adjacent ends of the manifold.

A further non-limiting embodiment of any of the foregoing examples includes a thermal shield arranged adjacent the sealed enclosure.

In a further non-limiting embodiment of any of the foregoing examples, the thermal shield includes a support and ceramic panels mounted in an array on the support.

In a further non-limiting embodiment of any of the foregoing examples, the ceramic panels include respective openings there-through and fasteners arranged partially within the respective openings and securing the ceramic panels on the support, and plugs arranged at least partially within corresponding ones of the openings.

In a further non-limiting embodiment of any of the foregoing examples, the sealed enclosure includes a heater.

In a further non-limiting embodiment of any of the foregoing examples, the sealed enclosure includes an insulator panel sealed against the plurality of tubes.

A method for use with a solar receiver according to an exemplary aspect of the present disclosure includes sealing an enclosure around a manifold that is connected with a plurality of tubes such that there is a volume between the enclosure and the manifold that is sealed from an exterior of the enclosure.

A further non-limiting embodiment includes substantially sealing the enclosure around the manifold from convective air flow with the exterior of the enclosure.

A further non-limiting embodiment of any of the foregoing examples includes establishing the volume to be at a lower pressure than the exterior.

In a further non-limiting embodiment of any of the foregoing examples, the volume has an insulating gas different than air.

In a further non-limiting embodiment of any of the foregoing examples, the insulting gas is selected from the group consisting of nitrogen-based gas, helium-based gas and carbon dioxide-based gas.

A thermal shield according to an exemplary aspect of the present disclosure includes a support and ceramic panels mounted in an array on the support. The ceramic panels include respective openings there-through. Fasteners are arranged partially within the respective openings and secure the ceramic panels on the support. Plugs are arranged at least partially within corresponding ones of the openings.

In a further non-limiting embodiment of any of the foregoing examples, the plugs are ceramic plugs.

In a further non-limiting embodiment of any of the foregoing examples, the ceramic panels include lap joints.

In a further non-limiting embodiment of any of the foregoing examples, the array is planar.

BRIEF DESCRIPTION OF THE DRAWINGS

The various features and advantages of the present disclosure will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows.

FIG. 1 shows an example solar power tower system.

FIG. 2 shows an example solar receiver system.

FIG. 3 shows portions of an example solar receiver.

FIG. 4A shows a sectioned view of a portion of a solar receiver.

FIG. 4B shows a perspective view of the solar receiver of FIG. 4A.

FIG. 4A shows another view of the solar receiver of FIG. 4A.

FIG. 5A shows a example of a thermal shield.

FIG. 5B shows another view of the thermal shield of FIG. 5A.

FIG. 5C shows a lap joint between ceramic panels of a thermal shield.

FIG. 6 shows a sectioned view of a ceramic panel.

DETAILED DESCRIPTION

Referring to FIG. 1, a solar power tower system 20 includes a high concentration solar receiver system 22 having a receiver assembly 24 coupled to a tower structure 25 at a predetermined height above ground to receive solar radiation S. A plurality of heliostats 26 focus the solar radiation S onto the receiver assembly 24.

Molten salt or other working fluid circulates, such as by pumping, from a cold storage tank system 28 through the solar receiver system 22. The heated working fluid then circulates to a hot storage tank system 30. When power is required, the hot working fluid is pumped to a steam generator system 32 to produce steam. The steam drives a steam turbine/generator system 34 that generates electricity for communication to a power grid. The working fluid is returned to the cold storage tank system 28 and is eventually reheated in the solar receiver system 22. It should be understood that although a particular arrangement is disclosed in the illustrated embodiment, any arrangement with a solar receiver system 22 will also benefit from this disclosure.

Referring to FIG. 2, the solar receiver system 22 generally includes a plurality of solar receivers 40 (shown schematically) that each include an upper cover assembly 42 and a lower cover assembly 44. The cover assemblies 42/44 protect a support structure 46 (FIG. 3) of the solar receiver 40 and any equipment therein from heliostat spillage that may miss the solar receivers 40. The solar energy from heliostat spillage can result in a heat flux of 300 kW/m² and a temperature of 1900° F./1038° C. or greater.

FIG. 3 shows selected portions of one of the solar receivers 40. In this example, each solar receiver 40 includes a plurality of tubes 50 that are connected with and extend between manifolds 52/54 for communicating the working fluid there through. The solar receiver 40 is generally vertically oriented such that the working fluid can be received into the manifold 52 and gravimetrically flow downward through the tubes 50 and into the manifold 54. The support structure 46 supports the tubes 50 and the manifolds 52/54. In this example, the tubes 50 include a thermal coating 56 over a heating zone Z that serves to absorb the solar radiation S and facilitate thermal transfer to the tubes 50 and working fluid. The manifolds 52/54 are laterally offset, or inboard, of the heating zone Z, to protect the manifolds 52/54 from exposure to solar radiation spillage.

The design of the tubes 50 also provides a relatively low number of different parts and reduces manufacturing costs and assembly or maintenance time. For example, the arrangement and geometry of the tubes 50 are symmetric about a vertical plane VP. Thus, each tube 50 has a corresponding tube 50 on an opposite side of the vertical plane VP that is a mirror image.

Any thermal losses from the solar receiver 40 can debit the overall efficiency of the solar receiver system 22. In this regard, as shown in FIGS. 4A, 4B and 4C, the solar receiver 40 includes a sealed enclosure 58 around the manifold 52 to insulate the manifold 52 from losing heat, prevent or limit freezing of the working fluid and generally provide a uniform temperature around the manifold 52 to prevent or limit hot spots that can otherwise damage the working fluid. Likewise, a similar sealed enclosure 58 can be provided around the manifold 54. The term “sealed” or variations thereof as used in this disclosure refers to structure that reduces convective air flow between the enclosure 58 and an exterior 62 (ambient) of the solar receiver 40. In a further example, the convective air flow is substantially eliminated.

The tubes 50 are connected to the manifold 52 by quick connectors (not shown). The quick connectors permit the tubes 50 to be easily removed and attached to the manifold 52. The tubes 50 extend through the sealed enclosure 58 and thus the sealed enclosure 58 surrounds the manifold 52 and a portion of the plurality of tubes 50. In this example, the sealed enclosure 58 includes a top wall 58 a above the manifold 52, a bottom wall 58 b below the manifold 52, a forward wall 58 c in front of the manifold 52, a back wall 58 d behind the manifold 52 and sidewalls 58 e/58 f adjacent the ends of the manifold 52. Thus, the sealed enclosure 58 surrounds the manifold 52 on all sides. The sealed enclosure 58 can be made of or include an insulating material, such as a ceramic material or flexible insulating material.

The forward wall 58 c includes an insulator panel 58 c′, such as an organic or polymeric panel, that is compressed against the outer surfaces of the tubes 50, to facilitate sealing and insulating. At least the inner surface of the insulator panel 58 c′ is in contact with the tubes 50 and may have grooves 59 that correspond to the shape of the tubes 50. The grooves 59 provide a close fit between the insulator panel 58 c′ and the tubes 50 for sealing and insulating.

The sealed enclosure 58 defines an interior volume 60 that is sealed from the exterior 62 of the solar receiver 40. To facilitate sealing, and also allow access to the interior volume 60, the sealed enclosure 58 includes seals 64 a/64 b. The seal 64 a is arranged between the top wall 58 a and the forward wall 58 c. The seal 64 b is arranged between the bottom wall 58 b and the tubes 50/forward wall 58 c. For example, the seal 64 b is compressed against the tubes 50 to provide a substantially air-tight closure that reduces convective gas flow between the interior volume 60 and the exterior 62. For example, there is no open, free gas flow between the interior volume 60 and the exterior 62 and any gas within the sealed enclosure 58 is substantially stagnant. The seals 64 a/64 b also provide the sealed enclosure 58 with compliance to accommodate thermal expansion and contraction from heating and cooling cycles, which facilitates maintaining the tubes 50 in a proper, sealed position.

The sealed, interior volume 60 thermally insulates the manifold 52 and a portion of the tubes 50 that are within the sealed enclosure 58. In one example, the interior volume 60 is evacuated and maintained at a pressure that is lower than the exterior 62. In another example, the interior volume 60, at the low pressure or at ambient pressure, includes an insulating gas. For example, the insulating gas is a helium-based gas, a carbon dioxide-based gas, a nitrogen-based gas or combinations thereof. In a further example, the environment in the interior volume 60 has a composition of greater than 90% by volume of the selected insulating gas. In a further example, the insulating gas has a composition that is different than air, which for purposes of this disclosure has a composition of 78% nitrogen, 21% oxygen, less than 1% argon, less than 0.05% carbon dioxide and a remainder of trace elements. The low pressure, and/or insulating gas, facilitates the reduction in thermal losses from the manifold 52 and portion of the tubes 50 that are within the sealed enclosure 58.

In this example, the sealed enclosure 58 also includes a heater 66 mounted on the bottom wall 58 b. In other examples, the heater 66 may be excluded, or additional heaters can be provided on other walls of the sealed enclosure 58. For example, the heater 66 is an electric resistance heater and is used to heat the interior volume 60 and manifold 52. The heater 66 can also be used to heat the manifold 52 for the purpose of preventing or limiting freezing of the working fluid in the manifold 52 and portion of the tubes 50 within the sealed enclosure 58.

As can be appreciated, the arrangement of the solar receiver 40 also embodies a method for use with the solar receiver 40. The method includes sealing the enclosure 58 around the manifold 52 (or alternatively the manifold 54) that is connected with the tubes 50 such that the interior volume 60 between the enclosure 58 and the manifold 52 is sealed from the exterior 62.

FIGS. 5A and 5B show perspective views of opposed sides of one of the cover assemblies 42. It is to be understood that the cover assembly 44 can be similarly constructed. In this example, the cover assembly 44, or thermal shield, includes a support 80, such as a metal frame, and ceramic panels 82 mounted in an array 84 on the support 80. The ceramic panels 82 can be made of an oxide composition, for example. The array 84 is a two-dimensional array that spans in a flat plane P. As shown in FIG. 5C, the ceramic panels 82 include a lap joint 86 between neighboring ceramic panels. The lap joint 86 provides a relatively loose fit between the neighboring ceramic panels 82 and thus permits the ceramic panels 82 to move relative to each other to accommodate thermal expansion and contraction.

Referring to FIG. 6, each of the ceramic panels 82 includes at least one opening 88 there through for mounting the ceramic panel 82 on the support 80. A fastener 90 is arranged partially within the respective opening 88 and secures the ceramic panel 82 on the support 80. A plug 92 is arranged at least partially within the opening 88 to protect the fastener 90 from the solar radiation S spillage. For example, the plug 92 is a ceramic plug and can be made of the same ceramic material composition as the ceramic panels 82.

Although a combination of features is shown in the illustrated examples, not all of them need to be combined to realize the benefits of various embodiments of this disclosure. In other words, a system designed according to an embodiment of this disclosure will not necessarily include all of the features shown in any one of the Figures or all of the portions schematically shown in the Figures. Moreover, selected features of one example embodiment may be combined with selected features of other example embodiments.

The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. The scope of legal protection given to this disclosure can only be determined by studying the following claims. 

What is claimed is:
 1. A solar receiver comprising: a manifold; a sealed enclosure around the manifold; and a plurality of tubes connected to the manifold and extending through the sealed enclosure.
 2. The solar receiver as recited in claim 1, wherein the sealed enclosure defines a volume between the sealed enclosure and the manifold, the sealed enclosure substantially sealing the volume from convective air flow between the volume and an exterior of the sealed enclosure.
 3. The solar receiver as recited in claim 2, wherein the volume is at a lower pressure than the exterior.
 4. The solar receiver as recited in claim 2, wherein the volume includes an insulating gas different than air.
 5. The solar receiver as recited in claim 4, wherein the insulating gas is selected from the group consisting of nitrogen-based gas, helium-based gas, carbon dioxide-based gas and combinations thereof.
 6. The solar receiver as recited in claim 1, wherein the sealed enclosure includes at least one seal element.
 7. The solar receiver as recited in claim 1, wherein the sealed enclosure includes at least one seal element between a panel of the sealed enclosure and the plurality of tubes.
 8. The solar receiver as recited in claim 1, wherein the sealed enclosure includes a top wall above the manifold, a bottom wall below the manifold, a forward wall in front of the manifold, a back wall behind the manifold, and side walls adjacent ends of the manifold.
 9. The solar receiver as recited in claim 1, further comprising a thermal shield arranged adjacent the sealed enclosure.
 10. The solar receiver as recited in claim 9, wherein the thermal shield includes a support and ceramic panels mounted in an array on the support.
 11. The solar receiver as recited in claim 10, wherein the ceramic panels include respective openings there-through and fasteners arranged partially within the respective openings and securing the ceramic panels on the support, and plugs arranged at least partially within corresponding ones of the openings.
 12. The solar receiver as recited in claim 1, wherein the sealed enclosure includes a heater.
 13. The solar receiver as recited in claim 1, wherein the sealed enclosure includes an insulator panel sealed against the plurality of tubes.
 14. A method for use with a solar receiver, the method comprising: sealing an enclosure around a manifold that is connected with a plurality of tubes such that there is a volume between the enclosure and the manifold that is sealed from an exterior of the enclosure.
 15. The method as recited in claim 14, including substantially sealing the enclosure around the manifold from convective air flow with the exterior of the enclosure.
 16. The method as recited in claim 15, including establishing the volume to be at a lower pressure than the exterior.
 17. The method as recited in claim 14, wherein the volume has an insulating gas different than air.
 18. The method as recited in claim 17, wherein the insulting gas is selected from the group consisting of nitrogen-based gas, helium-based gas and carbon dioxide-based gas.
 19. A thermal shield comprising: a support; ceramic panels mounted in an array on the support, the ceramic panels including respective openings there-through; fasteners arranged partially within the respective openings and securing the ceramic panels on the support; and plugs arranged at least partially within corresponding ones of the openings.
 20. The thermal shield as recited in claim 19, wherein the plugs are ceramic plugs.
 21. The thermal shield as recited in claim 19, wherein the ceramic panels include lap joints.
 22. The thermal shield as recited in claim 19, wherein the array is planar. 